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Why is there negative DMT modulus after tip sensitivity and spring constant is calibrated?

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psuxi posted on Wed, Aug 29 2012 10:23 AM

I calibrated the tip in ramp mode on clean hard surface first and then used it for imageing. I got DMT modulus mapping range from negative values to positive ones such as -2 MPa to 5 MPa.

Any one knows why this is happening? Is this DMT modulus mapping result meaningful at all?

Thanks!

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Verified by psuxi

That should not be possible unless you are using some kind of filter like a plane fit or a flatten on the data.  If you have not done anything to modify the data offline, please check and see if your "Offline planefit" in Nanoscope realtime is set to "Offset" or "Full".

Depending on the type of filter that was used, you may or may not be able to recover anything quantitative from the data.

One other thing, where are you finding the range of data?  If it is from the color bar, the real data range may not extend that low.  You can use Section to check for this.

--Bede

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Top 10 Contributor
280 Posts
Points 6,221
Bruker Employee
Verified by psuxi

That should not be possible unless you are using some kind of filter like a plane fit or a flatten on the data.  If you have not done anything to modify the data offline, please check and see if your "Offline planefit" in Nanoscope realtime is set to "Offset" or "Full".

Depending on the type of filter that was used, you may or may not be able to recover anything quantitative from the data.

One other thing, where are you finding the range of data?  If it is from the color bar, the real data range may not extend that low.  You can use Section to check for this.

--Bede

Top 75 Contributor
13 Posts
Points 153
psuxi replied on Wed, Aug 29 2012 7:57 PM

Thanks Bede!

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